[MATH-1300] BitsStreamGenerator#nextBytes(byte[]) is wrong

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.5
• Fix Version/s: 3.6
• Flags: Patch, Important
• Assignee: Unassigned
• Reporter: Rostislav Krasny
• Created: 19/Dec/15 01:57
• Updated: 25/Jan/16 20:28
• Resolved: 31/Dec/15 23:21

Description

Sequential calls to the BitsStreamGenerator#nextBytes(byte[]) must generate the same sequence of bytes, no matter by chunks of which size it was divided. This is also how java.util.Random#nextBytes(byte[]) works.

When nextBytes(byte[]) is called with a bytes array of length multiple of 4 it makes one unneeded call to next(int) method. This is wrong and produces an inconsistent behavior of classes like MersenneTwister.

I made a new implementation of the BitsStreamGenerator#nextBytes(byte[]) see attached code.

Issue Links

• is related to: MATH-1305 Improve performance of nextBytes() method of BitsStreamGenerator and AbstractRandomGenerator
• relates to: MATH-1304 "nextBytes" methods in RNG implementations